Conveyor belts are known which are provided with a belt core body, a front side cover rubber and a back side cover rubber laminated on the front surface and the rear surface of the belt core body, respectively, and an ear rubber arranged on both side sections of the belt core body in the width direction between these cover rubbers.
Conventionally, as a method for producing such a conveyor belt, a method is known which comprises the steps of: (1) mixing rubber material, (2) rolling and molding the belt core body, (3) rolling and molding the cover rubbers, (4) molding the ear rubber, (5) molding a conveyor belt by assembling each material supplied from each of the steps (2), (3), and (4) which are separately independent, (6) vulcanizing the formed conveyor belt, and (7) performing finishing on the conveyor belt after vulcanization.
The thickness of the conveyor belt which is the product to be finally obtained is the total of the thicknesses of the belt core body and the cover rubbers.
Because respective variations in the thicknesses of the belt core body, the cover rubbers, and the ear rubber are generated in the individual steps, there are limits in terms of reducing variations in the thickness of the conveyor belt to be finally molded.
If the thickness of the conveyor belt is excessive, defects are easily generated in the surface of the conveyor belt in the vulcanization step, in addition, there are disadvantages in that material is wasted and the production costs are increased.
Japanese Unexamined Patent Application Publication No. H05-301299A discloses extruding and rolling a cover rubber from a first extrusion rolling apparatus onto one side surface of a belt core body unwound from a core body unwinding stand, extruding and rolling a cover rubber from a second extrusion rolling apparatus onto the other side surface of the belt core body, contiguously vulcanizing the formed rubber sheet while contiguously supplying the sheet to correspond to the vulcanizing time of a continuous vulcanizer, and contiguously winding the vulcanized conveyor belt main body using a winding apparatus.
In the producing method described above in which the cover rubbers are contiguously rolled on the front surface and the rear surface of the belt core body, it is not specifically disclosed how variations in the thickness of the conveyor belt to be finally obtained are reduced.